The present invention relates to stabilizer compositions for polyvinyl chloride resins and to polyvinyl chloride resin compositions having improved resistance to degradation caused by heat. More particularly, the present invention relates to improved sodium perchlorate stabilizer compositions and their use in polyvinyl chloride resin compositions. Although capable of a variety of uses, this invention finds advantageously utility in providing improved long term stability at moderate temperatures to motor vehicle components shaped from polyvinyl chloride resin compositions, especially where the polyvinyl chloride resin compositions are used in combination with urethane.
The problem of imparting to polyvinyl chloride a sufficient heat processing stability at temperatures in which the polymer becomes sufficiently fluid or softened to permit shaping is of course of long standing, and has been satisfactorily resolved by addition to the polymer of various combinations of known heat stabilizers. At these temperatures, the resin can degrade, liberating hydrogen chloride, and discolor, become brittle, and stick to the equipment. These problems are overcome by combining with the polymer before heat processing or during heat processing one or more of the well established and successful conventional heat stabilizers, such as, for example, the well known organotin stabilizers and/or barium-cadmium or barium-zinc salt stabilizers.
Although the well established and successful conventional heat stabilizers provide effective stabilization to the polymer at elevated heat processing temperatures during standard processing, they may not provide effective stabilization to the polymer at lower more moderate temperatures after such heat processing. For example, protection against discoloration at moderate temperatures over long periods is a particular problem with motor vehicle components shaped from polyvinyl chloride resin compositions despite such compositions having contained conventional heat stabilizers during their heat processing. Depending upon their location in the vehicle, these components may be exposed to varied amounts of light, and also different rather high (above atmospheric) temperatures in use, and these differences can degrade motor vehicle components at differing rates. Additionally, when polyvinyl chloride resin compositions are associated with a polyurethane foam backing, e.g. automobile instrument panels, glove compartments, door handles, arm and head rests, the amine from the urethane can contribute to discoloration of the polyvinyl chloride resin composition.
A number of stabilizing systems have been proposed for imparting polyvinyl chloride resin articles molded with a polyurethane foam backing with resistance to deterioration from exposure to long term moderate heat and from exposure to an amine from urethane. For example, the art has recognized the use of perchlorate salts in polyvinyl chloride resin stabilization and in particular in stabilizing polyvinyl chloride that is used in contact with polyurethane foam or plastic. European Patent Application No. 86111174.8 discloses polyvinyl chloride resin stabilizer compositions comprising a 2, 2, 6, 6-tetramethyl piperidinyl compound and an ammonium or metal perchlorate. This publication also discloses the use of such stabilizer compositions for polyvinyl chloride resin articles molded with polyurethane foam backing.
U.S. Pat. No. 4,861,816 discloses polyvinyl chloride compositions containing a stabilizer mixture of certain barium/zinc carboxylic acid salts and a metal perchlorate and/or perchlorate ion type hydrotalcite. According to the '816 patent the perchlorate and perchlorate ion type hydrotalcite compound give excellent amine resistance particularly to urethane attached polyvinyl chloride sheets.
Perchlorates, however, are dangerous oxidizing materials and great care is needed in using them safely. Due to this hazard there may exist some reluctance in the industry to utilize perchlorate salts for polyvinyl chloride resin stabilization. Accordingly, there exists a need for a perchlorate stabilizer composition of reduced hazard level. Additionally, there exists a need for improved perchlorate salt stabilizer compositions for polyvinyl chloride resin compositions exposed to long term, above ambient temperatures, especially when such compositions are in contact with urethane.
Accordingly, a general object of the present invention is to provide an improved perchlorate salt stabilizer composition.
It is another object of the present invention to provide a perchlorate salt stabilizer composition of reduced hazard level.
It is another object of the present invention to provide a method of stabilizing halogen-containing organic or polymer resin compositions particularly those in contact with urethane, against long term above-ambient temperature degradation.
It is a further object of the present invention to provide novel stabilized halogen-containing polymers.
It is a further object of the present invention to provide shaped motor vehicle components having an improved stability at moderate temperatures.
These and other objects of the present invention will be apparent to those skilled in the art from the following description.